I consider it anything that doesn't take place in the user's browser. Writing the APIs, interacting with the DB, defining the backend data models, dreaming up t

I consider it anything that doesn't take place in the user's browser. Writing the APIs, interacting with the DB, defining the backend data models, dreaming up the microservice architecture, whatever your workplace is doing. If it's not responsible for generating HTML, CSS, or JS, I don't really consider it front end.